The present invention relates to liquid degassing, and more particularly to a multitude of flow impingement elements which are interleaved to provide a fuel channel with intricate two-dimensional flow characteristics that enhance mixing and oxygen transport.
Jet fuel is often utilized in aircraft as a coolant for various aircraft systems. The presence of dissolved oxygen in hydrocarbon jet fuels may be objectionable because the oxygen supports oxidation reactions that yield undesirable by-products. Solution of air in jet fuel results in an approximately 70 ppm oxygen concentration at the equilibrium saturation condition. When aerated fuel is heated between approximately 300° F. and 850° F. the dissolved oxygen initiates free radical reactions of the fuel resulting in deposits commonly referred to as “coke” or “coking.” Coke may be detrimental to the fuel system and may inhibit combustion. The formation of such deposits may impair the normal functioning of a fuel system, either with respect to an intended heat exchange function or the efficient injection of fuel.
Various systems are currently available for liquid deoxygenation. However, none are capable of processing high flow rates characteristic of aircraft engines in a compact and lightweight assembly, and lowering dissolved oxygen concentration sufficiently to suppress coke formation. Typically, lowering the oxygen concentration to approximately 5 ppm is sufficient to overcome the coking problem and allows the fuel to be heated to approximately 650° F. during heat exchange, for example. Moreover, it is often desirable to further reduce the oxygen concentration to allow heating of the fuel to even higher temperatures.
One Fuel Stabilization Unit (FSU) intended for use in aircraft removes oxygen from jet fuel by producing an oxygen partial pressure gradient across a membrane permeable to oxygen. The FSU includes a plurality of flow plates sandwiched between permeable membranes and porous substrate plates within a housing. Each flow plate defines a portion of the fuel passage and the porous plate backed permeable membranes define the remaining portions of the fuel passages.
The planar flow plates utilize flow impingement elements to enhance contact between fuel flow and the oxygen permeable membrane to increase mass transport of dissolved oxygen. Design of the flow impingement elements poses relatively complicated fluid dynamic issues as the flow impingement elements need to enhance contact between fuel flow and the oxygen permeable membrane yet minimize the effect on fuel flow pressure passing therethrough. Furthermore, the flow impingement elements must not unduly increase the fuel flow path length which may result in a significant increase in the size and weight of the FSU system.
Accordingly, it is desirable to provide for the deoxygenation of hydrocarbon fuel in a size and weight efficient system that increases deoxygenation while minimizing fuel flow pressure drop.